Delineating neck targets for intensity-modulated radiation therapy of head and neck cancer.

Experience with intensity-modulated radiation therapy (IMRT) for head and neck cancer is building greater understanding of the requirements for therapy planning. Delineation of the lymphatic targets for IMRT of the head and neck is a crucial step in this planning, and often determines the risks of marginal or out-of-field local/regional tumor recurrence. Definition of the gross tumor volumes needs to take into account both radiological (CT, MRI, PET) and clinical findings. Understanding of the appropriate CTVs is developing based on: (a) established knowledge of the natural history and spread patterns of head and neck cancer, (b) the accruing experience of clinicians using IMRT, and (c) evaluations of patient outcomes following consistent treatment approaches as determined by institution practice patterns and prospective clinical studies. This chapter will outline the important steps in lymphatic target definition for head and neck cancer, and will discuss several special clinical concerns for these patients and their management.